Damper with pressure-sensitive compression damping

ABSTRACT

A damper includes a piston rod, a damping piston, at least one cylinder containing a damping liquid, a fixed partition member for partitioning the interior of the damper into two liquid chambers, a pressure source, and a valve in communication with the pressure source which reacts as a function of the pressure. The valve can also be in communication with additional forces, such as mechanical spring forces, which can be adjustable. The valve can include a pressure intensifier. The valve generates fluid flow resistance during flow of liquid in a first direction through the partition member. The fluid flow resistance in the first direction varies according to the amount of force communicated to the valve by the pressure source and any additional forces. The partition member can include means for providing low-resistance return flow of liquid in a second direction.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No.11/261,051, filed 27 Oct. 2005, which is a continuation of InternationalApplication No. PCT/US2004/038661, filed 18 Nov. 2004, which is acontinuation of U.S. application Ser. No. 10/661,334 (now abandoned),filed 12 Sep. 2003, which claims priority to Provisional Application No.60/485,485, filed 8 Jul. 2003, the entireties of which are herebyincorporated by reference herein and made a part of this specification.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to a damper and, more particularly, to a dampersuitably used as a shock absorber or front fork on the suspension of abicycle, motorcycle, automobile or other vehicle.

2. Description of the Related Art

Dampers (shock absorbers, MacPherson struts, front forks, etc.) forcontrolling vehicle body motion and handling characteristics duringvehicle travel over uneven surface are well-known in the art. Damperstypically comprise a closed hydraulic cylinder with an internal pistonconnected to a central piston rod, which reciprocates within thecylinder to produce damping forces.

As is well known in the art, the damping forces created by a damper havea major influence on the overall dynamic performance of a vehicle. Awide range of dynamic conditions are encountered during typical vehiclemotion over various surfaces and terrain features. For example, thesefeatures and conditions include large and small bumps, sharp-edged bumpsand round-edged bumps, close-spaced bumps and widespaced bumps, stutterbumps and gradual undulating bumps, and so forth. In addition,conditions include vehicle acceleration and deceleration modes, uphilland downhill travel modes, as well as turning modes.

Besides the factors noted above, different operators of a specificvehicle traversing identical terrain features often prefer significantlydifferent damping characteristics. This is especially true forlight-weight vehicles, such as bicycles or motorcycles, where riderweight can be a major portion of total weight, and where rider “style”or “technique” can have a significant influence on overall suspensionperformance.

SUMMARY OF THE INVENTION

The present invention provides an improved damper which providesautomatic modulation of damping forces based on sensing and reacting tointernally-generated or externally-generated conditions.

In one embodiment, a damper generates a compression damping rate that ismodulated in accordance with an internally-generated pressure. Anexample of an internally-generated pressure is the air or nitrogenpressure found in the wide-variety of conventional “DeCarbon-type”pressurized dampers as have been known in the art for 40 years(reference U.S. Pat. No. 3,101,131 to DeCarbon, issued in 1963).

In another embodiment, a damper generates a compression damping ratethat is modulated in accordance with an externally-generated pressure.An example of an externally-generated pressure would be the pressurethat could be created at an end fitting of a compressed externalcoil-over spring.

In another embodiment, a damper generates a compression damping ratethat is modulated in accordance with an independently-regulatedpressure. An example of an independently-regulated pressure would be apressure source controlled by computer and supplied to the shockabsorber. The computer may utilize input from various sensors on thevehicle (for example sensors monitoring vehicle speed and acceleration,as well as the relative positions and velocities of the sprung andunsprung masses) and continuously regulate the pressure supplied to theshock absorber in accordance with a pre-determined algorithm.

In another embodiment, a damper having damping features may be quicklyand easily tuned and adjusted by simply rotating one or morereadily-accessible external knobs or levers. Turning an external knob(or knobs) is quick and easy and thus can be done in a routine“on-the-fly” manner frequently during the ride. Since terrain and trailconditions constantly change, this greatly benefits the rider byenabling him/her to continuously select the best damping characteristicsfor the current situation.

In another embodiment, a damper includes valving structures directlyadjoining, or within, a fixed partition member in the damper thatpartitions a portion of the damper interior into two liquid chambers.The valving structures specifically do not directly adjoin, or comprisepart of, the main damping piston connected to the piston rod of thedamper. The valving structures react as a function of internal orexternal pressures to provide damping forces by restricting fluid flowin one direction through the fixed partition member.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a sectional front view of a prior-art embodiment of apressurized damper unit.

FIG. 2 is a sectional front view of the prior-art damper of FIG. 1modified in accordance with an exemplary embodiment of the presentinvention.

FIG. 3 is an enlarged partial sectional front view of the damper of FIG.1, showing the added structure of this embodiment of the presentinvention.

FIG. 4 is a sectional front view of the prior-art damper of FIG. 1modified in accordance with a second exemplary embodiment of the presentinvention.

FIG. 5 is an enlarged partial sectional front view of the damper of FIG.4, showing the added structure of this embodiment of the presentinvention.

FIG. 6 is a sectional view of the damper of FIG. 5, taken throughsection A-A of FIG. 5.

FIG. 7 is a sectional front view of the damper of FIG. 4, showing shaftdisplacement fluid flow through the fixed partition member during anextension stroke of the damper.

FIG. 8 is a sectional front view of the damper of FIG. 4, showing shaftdisplacement fluid flow through the intensifier valve during acompression stroke of the damper.

FIG. 9 is a sectional front view of the damper of FIG. 4 modified inaccordance with a third exemplary embodiment of the present invention,with the intensifier valve structure moved to the upper end of thedamper cylinder, with a remote reservoir assembly added, and with thefloating piston re-located from the damper cylinder to the reservoircylinder.

FIG. 10 is a sectional front view of the prior-art damper of FIG. 1,modified in accordance with a fourth exemplary embodiment of the presentinvention, with the upper eyelet replaced by a piggyback eyelet with anattached reservoir cylinder, with the floating piston re-located fromthe damper cylinder to the reservoir cylinder, and with the intensifierassembly located in the upper end of the reservoir cylinder.

FIG. 11 is an enlarged partial sectional front view of the damper ofFIG. 10, showing the added structure of this embodiment of the presentinvention.

FIG. 12 is a sectional front view of the damper of FIG. 10, showing thisembodiment with the addition of an external intensifier adjusting screw.

FIG. 13 is an enlarged partial sectional front view of the damper ofFIG. 12.

FIG. 14 is a sectional front view of the damper of FIG. 10, with a fifthexemplary embodiment of the present invention located in the upper endof the reservoir cylinder.

FIG. 15 is an enlarged partial sectional front view of the damper ofFIG. 14.

FIG. 16 is a sectional front view of the damper of FIG. 10, with a sixthexemplary embodiment of the present invention located in the upper endof the reservoir cylinder.

FIG. 17 is an enlarged partial sectional front view of the damper ofFIG. 16.

FIG. 18 is a sectional front view of the prior-art damper of FIG. 1modified in accordance with a seventh exemplary embodiment of thepresent invention.

FIG. 19 is an enlarged partial sectional front view of the damper ofFIG. 18, showing the added structure of this embodiment of the presentinvention.

FIG. 20A is a sectional front view of the prior-art damper of FIG. 1modified in accordance with an eighth exemplary embodiment of thepresent invention.

FIG. 20B is an alternate version of the damper of FIG. 20A with modifiedstructure to provide a first alternate shape to the compression dampingcharacteristic produced by the exemplary embodiment of FIG. 20A.

FIG. 20C is an alternate version of the damper of FIG. 20A with modifiedstructure to provide a second alternate shape to the compression dampingcharacteristic produced by the exemplary embodiment of FIG. 20A.

FIG. 21 is an enlarged partial sectional front view of the damper ofFIG. 20A, showing the added structure of this embodiment of the presentinvention.

FIG. 22 is a sectional front view of the prior-art damper of FIG. 1,modified in accordance with a ninth exemplary embodiment of the presentinvention, including elimination of the floating piston.

FIG. 23 is an enlarged partial sectional front view of the damper ofFIG. 22, showing the added structure of this embodiment of the presentinvention.

FIG. 24 is a sectional front view of the prior-art damper of FIG. 1,modified in accordance with a tenth exemplary embodiment of the presentinvention, including elimination of the floating piston and addition ofan intensifier preload spring.

FIG. 25 is an enlarged partial sectional front view of the damper ofFIG. 24, showing the added structure of this embodiment of the presentinvention.

FIG. 26 is a sectional view of the damper of FIG. 25, taken throughsection A-A of FIG. 25.

FIG. 27 is an enlarged partial sectional front view of the damper ofFIG. 24, modified in accordance with an eleventh exemplary embodiment ofthe present invention, including elimination of the intensifier preloadspring and addition of an intensifier open-bias spring.

FIG. 28 is a sectional front view of an air-sprung bicycle shockabsorber, modified in accordance with a twelfth exemplary embodiment ofthe present invention.

FIG. 29 is a sectional front view of the prior-art damper of FIG. 1,modified in accordance with a thirteenth exemplary embodiment of thepresent invention.

FIG. 30 a sectional front view of the prior-art damper of FIG. 1modified in accordance with a fourteenth exemplary embodiment of thepresent invention.

FIG. 31 is an enlarged partial sectional front view of the damper ofFIG. 30, showing the specific structure of this embodiment of thepresent invention.

FIG. 32 is a sectional front view of a modified version of the damper ofFIG. 30, incorporating a fifteenth exemplary embodiment of the presentinvention.

FIG. 33 is an enlarged partial sectional front view of the damper ofFIG. 32, showing the specific structure added to this embodiment of thepresent invention.

FIG. 34 is an overall perspective view of the front fork of a bicycle.

FIG. 35 is an overall sectional front view of one leg of the fork ofFIG. 34, incorporating a sixteenth exemplary embodiment of the presentinvention.

FIG. 36 is a sectional front view of the damper assembly of the fork legof FIG. 35.

FIG. 37 is an enlarged partial sectional front view of the damper ofFIG. 36, showing the specific structure of this embodiment of thepresent invention.

DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS

The prior-art damper 100 of FIG. 1 will be described first, in order toprovide a point of departure for better understanding the improvementsof the present invention, which will be described further on. It is tobe understood, of course, that this specific prior-art embodiment isrepresentative only, and that the embodiments disclosed herein may beapplied to other types of dampers.

In FIG. 1 the prior-art damper 100, as is known to those skilled in theart, is comprised of an upper eyelet 110 and a lower eyelet 112 forattachment to, for example, the sprung and un-sprung portions of avehicle (not shown). The lower eyelet 112 is connected to the piston rod120 which passes through the seal head 130 and has a damping piston 140attached at the other end. The damping piston 140 reciprocates in thedamper cylinder 150 as the sprung and unsprung portions of the vehiclemove relative to each other when, for example, the vehicle traversesuneven terrain. The damping piston 140 has rebound valving 141 (shownsymbolically here) and compression valving 142 (also shown symbolically)for restricting fluid flow during rebound strokes (lengthening) andcompression strokes (shortening). The valving produces damping forcesthat resist the imposed motion. For example, the valving structures maybe flexible stacks of disc valves covering flow ports through thedamping piston 140, suitable for a variety of applications andcondition.

Still referring to FIG. 1, the damper cylinder 150 is sealed at one endby the seal head 130 and at the other end by the upper eyelet 110. Afloating piston 160 is sealingly engaged, but free to reciprocate,toward the upper end of the damper cylinder 150. The floating piston 160separates the hydraulic fluid 170 below it from theinternally-pressurized chamber 180 above it, which contains apressurized gas (for example, nitrogen or air). The Schrader valve 190provides access to the internally-pressurized chamber 180, which forms apressure source.

The damping piston 140 divides the total amount of hydraulic fluid 170contained in the damper cylinder 150 into two portions: a portion abovethe damping piston 140 (i.e., compression chamber 150 a), and a portionbelow it (i.e., rebound chamber 150 b). When the damping piston 140moves upward in the damper cylinder 150 (a compression stroke) some ofthe hydraulic fluid 170 in the compression chamber 150 a flows downwardthrough the damping piston 140, via the compression valving 142, intorebound chamber 150 b. The compression valving 142 restricts this flow,creating compression damping.

When the damping piston 140 moves downward in the damper cylinder 150 (arebound stroke) some of the hydraulic fluid 170 below the damping piston140 must flow upward through the damping piston 140, via the reboundvalving 141, into the area above the damping piston 140. The reboundvalving 141 restricts this flow, creating rebound damping.

In order to understand the operation of the exemplary embodiments, it isalso important to clearly understand the movement of the floating piston160, and of the hydraulic fluid 170 below it, during an inward oroutward movement of the piston rod 120. Specifically, it is important tounderstand the flow of hydraulic fluid 170 that occurs due to theadditional volume displaced by the piston rod 120 as it enters thedamper cylinder 150, as well as the flow that occurs due to the volumevacated by the piston rod 120 as it is withdrawn from the dampercylinder 150.

During a compression (upward) stroke such as described above, the pistonrod 120 moves further into the damper cylinder 150, thus occupying moreof the total available internal volume of the damper cylinder 150. Thevolume occupied by the additional length of the piston rod 120 thatenters the damper cylinder 150 displaces an equal volume of thehydraulic fluid 170, which moves upward and is accommodated by an upwardmovement of the floating piston 160. This decreases the volume of theinternally-pressurized chamber 180 above the floating piston 160, whichcorrespondingly increases the pressure somewhat. The net effect is thatthe added volume of the entering piston rod 120 is accommodated by anequally decreased volume of the internally-pressurized chamber 180.

During a rebound (outward) stroke the effects described above arereversed. In this case, since the piston rod 120 is being withdrawn, itoccupies less of the total available internal volume of the dampercylinder 150. The space vacated by the withdrawn piston rod 120 isfilled by the hydraulic fluid 170 which is urged downward by thepressure above the floating piston 160 to fill the vacated space. In sodoing, the floating piston 160 moves downward, increasing the volume ofthe internally-pressurized chamber 180 above it, which correspondinglyreduces the pressure somewhat.

The above-described principles of operation for a conventionalDeCarbon-type single-tube, pressurized damper such as shown in FIG. 1are well-known to those skilled in the art.

Referring now to FIGS. 2 and 3, additional structure in accordance witha first exemplary embodiment of the present invention is shown added tothe prior-art damper 100 of FIG. 1. Since the structure and function ofseveral of the parts in FIGS. 2 and 3 are substantially identical tothose in FIG. 1, the corresponding parts are designated by the samereference numbers as in FIG. 1. (This also generally applies to allother FIGS. which follow.) A partition 210 is secured within the bore ofthe damper by a partition retaining ring 211. This partition 210physically divides the hydraulic fluid into one portion above thepartition 210, and another portion below it. The partition 210 has aplurality of rebound flow ports 220 covered by a check valve 230 whichis lightly biased in contact with the partition 210 by a relatively softcheck valve spring 231. Additionally, the partition 210 has a centralcompression flow port 240 which, in the position illustrated in FIG. 3,is blocked at its upper end by the small end of an intensifier piston250.

The intensifier piston 250 is located within an intensifier housing 260,which can be integral with the damper cylinder 150 (as shown), or can bea separate structure sealed and retained within the bore of the dampercylinder 150. During upward movement of the intensifier piston 250 asoccurs during operation (to be described in detail further on), theintensifier piston 250 is prevented from exiting the intensifier housing260 by the intensifier retaining ring 251. The intensifier piston issealingly engaged with the intensifier housing 260 at its upper (largediameter) end, as well as at its lower (smaller diameter) end. There isat least one vent port 270 which vents the space between the upper andlower seals of the intensifier piston 250 to outside atmosphericpressure. There is also at least one bi-directional flow port 280 whichpasses vertically through intensifier housing 260.

Still referring to FIGS. 2 and 3, the principles of operation of thepresent embodiment are described in the following paragraphs.

During a rebound stroke, the piston rod 120 is withdrawn from the dampercylinder 150, resulting in some amount of vacated volume toward thelower end of the damper cylinder 150. As described previously, thisresults in downward movement of the floating piston 160, as well as adownward flow of the hydraulic fluid 170 immediately below it. Sincedownward movement of the floating piston 160 reduces the space betweenthe floating piston 160 and the partition 210, and since hydraulic fluidis incompressible, hydraulic fluid flows down through the bi-directionalflow port(s) 280. It then flows down through the partition 210 via therebound flow port(s) 220. It does this by opening the check valve 230against the relatively light resistance of the check valve spring 231.

During a compression stroke, the piston rod 120 and the damping piston140 move further into the damper cylinder 150, thus displacing a volumeof the hydraulic fluid 170 equal to the volume of the additional lengthof the piston rod 120 which enters the damper cylinder 150. As describedpreviously, this results in an upward flow of the displaced volume ofhydraulic fluid, accommodated by an upward movement of the floatingpiston 160, which somewhat decreases the volume, and increases thepressure, in the internally-pressurized chamber 180. However, in orderto do so, the displaced volume of hydraulic fluid must first passthrough the partition 210. To achieve this, the fluid must create anupward force (pressure) at the lower (small) end of the intensifierpiston 250 which is sufficient to overcome the downward force (pressure)at the upper (large) end of the intensifier piston 250. To do sorequires a pressure at the lower end of the intensifier piston 250 thatis greater than the pressure at the upper end of the intensifier piston250 by a multiple approximately equal to the ratio of thecross-sectional area of the large end of the intensifier piston 250 tothe cross-sectional area of the compression flow port 240.

For simplicity, it is assumed that the diameter of the small end of theintensifier piston 250 is only slightly greater than the diameter of thecompression flow port 240. Thus, the annular contact area between theseparts is relatively quite small, and it can be said that, for flowthrough the compression flow port 240, a pressure is required at thelower end of the intensifier piston 250 that is greater than thepressure at the upper end of the intensifier piston 250 by a multipleapproximately equal to the ratio of the area of its large end divided bythe area of its small end.

This pressure differential (multiple) between the small end and largeend of the pressure intensifier 250 creates a compression damping effectin the damper.

Here is an example. Assume the diameter of the large end of theintensifier piston 250 is twice the diameter of the small end, and thusthat the ratio of their cross-sectional areas is 4:1. Assume thediameter of the piston rod 120 is O½″, and thus it has a cross-sectionalarea of about 0.2 square inches. Assume the damping piston 140 hastraveled inward into the damper cylinder 150 some distance (i.e., it isnot fully-extended or “topped-out” against the seal head 130), as shownin FIG. 2. Assume that the pressure of the internally-pressurizedchamber 180 above the floating piston is 100 psi. Assume staticconditions, with the damping piston 140 not moving. Given theseassumptions, and based on elementary principles, there is a uniformpressure of 100 psi throughout the interior of the damper. Furthermore,it can be readily calculated that, under these static conditions, the100 psi internal pressure acting on the 0.2 square inch cross-sectionalarea of the piston rod 120 creates a 20-pound force tending to extendthe piston rod 120. In racing circles, this 20-pound force is sometimesreferred to as “static nose force”.

The above described static conditions. Now the compression dampingeffect produced by the intensifier piston 250 during a compressionstroke (inward movement of the piston rod 120) is described. Per basicprinciples, for an intensifier piston 250 with a cross-sectional arearatio of 4:1, a pressure of approximately 400 psi at the small end isrequired to overcome the 100 psi pressure at the large end (whichoriginates from the internally-pressurized chamber 180 above thefloating piston 160), in order to cause the intensifier piston 250 tomove upward, thus unblocking the compression flow port 240 and allowingupward flow of the hydraulic fluid 170 displaced by the inward movementof the piston rod 120.

For simplicity, it is assumed in the following discussion that thedamping piston 140 has several large thru-holes and no restrictivevalving (note that, actually, the exemplary embodiments of the presentinvention generally do incorporate restrictive valving on the dampingpiston 140 which does create compression damping forces). In otherwords, for purposes of clarity in describing the basic principles of thepresent embodiment, it is assumed here that the damping piston 140itself creates no compression damping forces. Now, the 400 psi pressurecreated at the small end of the intensifier piston 250 acts uniformlythroughout all portions of damper cylinder 150 below the intensifierpiston 250. Acting on the 0.2 square inch cross-sectional area of thepiston rod 120, it creates an 80-pound “dynamic nose force”. Thedifference between the previous 20-pound “static nose force” and this80-pound “dynamic nose force” is 60 pounds; this 60 pounds representsthe compression damping force produced by the present embodiment.Increasing the diameter and cross-sectional area of the piston rod 120,of course, would create an even greater damping force.

To further describe the principles of the present embodiment, in thefollowing it will be assumed that the above compression stroke continuesinward for a distance sufficient to move the floating piston 160 upwardsome amount and increase the pressure in the internally-pressurizedchamber 180 from 100 psi to 150 psi. This 150 psi pressure, of course,acts on the large end of the intensifier piston 250 and nowapproximately 600 psi pressure (basic 4:1 ratio) is required at thesmall end of the intensifier piston 250 in order for it to remain open,allowing continuation of the compression stroke. With 600 psi now actingon the 0.2 square inch cross-sectional area of the piston rod 120 a120-pound “dynamic nose force” is now produced. In other words, as thecompression stroke continues and the damping piston 140 and piston rod120 travel further into the damper cylinder 150, the volume of hydraulicfluid displaced by the piston rod 120 causes the floating piston 160 tomove upward, which increases the pressure in the internally-pressurizedchamber 180, which increases the compression damping effect produced bythe present embodiment.

Put another way, the present embodiment produces a “position-sensitive”compression damping effect, with the compression damping forceincreasing as the piston rod 120 and the damping piston 140 move furtherinto the damper cylinder 150. The extent and degree of thisposition-sensitive effect is influenced by the pre-set volume of theinternally-pressurized chamber 180 above the floating piston 160,relative to the diameter and maximum available travel of the piston rod120. If the pre-set volume of the internally-pressurized chamber 180 isrelatively large, the position-sensitive effect is reduced. If thepre-set volume is relatively small, the position-sensitive effect isincreased.

FIGS. 4, 5, and 6, show another exemplary embodiment of the presentinvention. This embodiment differs from the previous embodiment of FIGS.2 and 3 primarily due to an alternate configuration of the intensifierpiston 255, as best seen in FIG. 5. As compared with the previous“solid” intensifier piston 250 of FIG. 3, the intensifier piston 255 ofFIG. 5 has an intensifier piston compression flow port 256 which passesthrough its center. Another difference is the addition of an intensifierbleed screw 257 instead of the vent port 270 in FIG. 3. During assemblyof the intensifier piston 255 into the partition 262, this featureenables any trapped air pressure in the space between the upper andlower seals of the intensifier piston 255 to be vented by removing theintensifier bleed screw 257. It further enables said space to be sealedoff again, to provide proper operation, by re-installing said screw.This is done as part of the final assembly of these components.

Still referring to FIG. 5, the intensifier retaining ring 258 utilizedhere differs in form, but not function, from the previous intensifierretaining ring 251 of FIG. 3, Similarly, the check valve 235, the checkvalve spring 236, and the rebound flow port 222 as shown in FIG. 5 alldiffer in form, but not function, from the equivalent featuresillustrated in FIG. 3.

One practical advantage of the embodiment of FIG. 5 as compared with theembodiment of FIG. 3 is that it combines the functions of both thepartition 210 and the intensifier housing 260 of FIG. 3 into onecomponent, the partition 262 of FIG. 5. This reduces total part countand cost of the damper unit.

In operation during a compression stroke, fluid displaced by inwardmovement of the piston rod 120 applies pressure to the small end of theintensifier piston 255 via the arc flow port(s) 245. Similar to theprinciples of operation of the previous embodiment, the intensifierpiston 255 moves upward to permit upward flow of hydraulic fluid whenthe pressure ratio between the small end and the large end equals thearea ratio of the large and small ends. For the intensifier piston 255of FIG. 5, this statement refers specifically to the annular areas ofthe large and small ends.

Here is an example. Assume the ratio of the annular area at the largeend of the intensifier piston 255 to the annular area at the small endis 2:1. Also assume that the nitrogen in the internally-pressurizedchamber 180 above the floating piston 160 exerts a downward pressure of100 psi on the annular area at the large end of the intensifier piston255. Given these parameters, and in accordance with basic principles, apressure of 200 psi must be applied to the annular area at the small endof the intensifier piston 255 in order to cause the intensifier piston255 to move upward and permit upward flow of the displaced hydraulicfluid through the intensifier housing arc port(s) 245, and then upthrough the intensifier piston compression flow port 256.

FIG. 7 illustrates the shaft displacement rebound fluid flow 270 thatoccurs through the structure of FIG. 5 during a rebound stroke of thedamper. Similarly, FIG. 8 illustrates the shaft displacement compressionfluid flow 271 that occurs during a compression stroke of the damper.

FIG. 9 shows another exemplary embodiment of the present invention. Thisembodiment is similar to the previous embodiment shown in FIGS. 4, 5, 6,7, and 8, except that a remote reservoir assembly 310 has been added.Also, the intensifier assembly 330 has been moved upward to the upperend of the damper cylinder 150. The remote reservoir assembly 310 isconnected to the main damper cylinder assembly 320 by an hydraulic hose340. The remote reservoir assembly 310 includes a reservoir end fitting312, a reservoir cylinder 314, a floating piston 160, and a reservoircap 316.

One advantage of the embodiment of FIG. 9 as compared with previousembodiments is that, for a given length of damper cylinder 150 itincreases the available travel distance of the damping piston 140(available “damper stroke”).

FIGS. 10 and 11 show a exemplary embodiment of the present inventioncomprising a piggyback eyelet 410 with an attached reservoir cylinder314 containing a floating piston 160 and an intensifier assembly 420.The function of the partition 421, the check valve 422, the check valvespring 423, and the rebound flow port 424 of this embodiment are similarto the corresponding structures of the previous embodiment shown in FIG.3. The compression flow port 425 in the partition 421 provides acompression flow path for fluid from the damper cylinder 150 to anupward-facing annular area of the intensifier piston 426. Due to thepiston seal 427 and the vent 428 provided, the two other upward-facingareas of the intensifier piston 426 are at atmospheric pressure(considered zero pressure for purposes of this description). The largearea of the bottom face of the intensifier piston 426 is subjected tothe pressure within the internally-pressurized chamber 180 below thefloating piston 160. The intensifier piston 426 is fitted with anintensifier retaining ring 429 to ensure that it remains within thepartition 421 during assembly and other possible conditions.

Similar to the principles of operation described for previousembodiments of the present invention, under static conditions theintensifier piston 426 is urged upward by the pressure on its bottomface into firm, sealing contact with the partition 421. The intensifierpiston 426 remains in firm sealing contact with the partition 421 unlessthe fluid pressure from the compression flow port 425 exerted downwardagainst the upward-facing annular area 430 of the intensifier piston 426creates sufficient force to overcome the upward force exerted bypressure on the bottom face of the intensifier piston 426. This requiresthat pressure in the compression flow port 425 equals a multiple of thepressure in the internally-pressurized chamber 180; said multiple beingapproximately equal to the ratio of the area of the bottom face of theintensifier piston 426 to the area of the upward-facing annular area 430of the intensifier piston 426.

The relationship noted above is approximate only, due to the relativelynarrow annular overlap area where the intensifier piston 426 contactsthe partition 421. During operation, when the intensifier piston 426moves downward, and downward compression fluid flow occurs, thecompression fluid pressure acting downwardly on this generally narrowannular edge portion of the overall upward-facing annular area 430 ofthe intensifier piston 426 is somewhat reduced in accordance withBernoulli principles.

Similar also to previous embodiments: the increased pressure that isrequired to urge the intensifier piston 426 downward, to permit flow ofthe displaced fluid, acts on the cross-sectional area of the piston rod120, thus creating a compression damping force.

FIGS. 12 and 13 show a modified version of the embodiment of FIGS. 10and 11 which provides external adjustability of the compression dampingforce produced by the intensifier assembly 440. This modified embodimentincludes an intensifier adjusting screw 441, an adjuster piston 442, andan adjuster coil spring 443. In operation, rotation of the intensifieradjusting screw 441 increases or decreases the preload force on theadjuster coil spring 443. This force is transmitted through the adjusterpiston 442 as an increased or decreased pressure in the adjacenthydraulic fluid 445. This increased or decreased pressure iscommunicated to the upward-facing areas of the intensifier piston 446with which the hydraulic fluid 445 is in contact. The downward forcethus created on the intensifier piston 446 reduces, to a greater orlesser degree depending on the specific adjustment of the preload forceon the adjuster coil spring 443, the compression fluid pressure requiredto cause the intensifier piston 446 to move downward to permitcompression fluid flow. Thus, this adjustment mechanism alters thecompression damping force which is experienced at the piston rod 120.

FIGS. 14 and 15 show another exemplary embodiment of the presentinvention. This embodiment utilizes an intensifier assembly 460structure similar to that of FIGS. 2 and 3, but incorporated into theupper end of a reservoir cylinder 314 similar to that of FIGS. 10 and11. The principles of operation for this embodiment are identical tothose previously described for FIGS. 2 and 3.

FIGS. 16 and 17 show yet another exemplary embodiment of the presentinvention. This embodiment utilizes an intensifier assembly 510 similarto that of FIGS. 14 and 15, but, in addition, provides externaladjustability via an intensifier adjuster knob 512. The principles ofoperation for this embodiment are similar to those previously describedfor FIGS. 14 and 15, except for operation of the adjuster structurewhich is described in the following.

As best seen in FIG. 17, an external rotatable intensifier adjuster knob512 is secured to a freely-rotating hex driver shaft 514 which includesa downwardly-projecting male hex portion which is keyed into a femalehex portion of a threaded spring base 516 which rotates with it. Theintensifier adjuster knob 512 is fitted with at least one detent ball518 and one detent spring 519 which provide a detent function byproviding audible and tactile feedback for each quarter turn (forexample) adjustment of the intensifier adjuster knob 512, as well as byhelping to secure it at any pre-set position. The threaded spring base516 is threaded on its outside diameter to produce axial movement uponrotation. Depending on the direction of rotation of the intensifieradjuster knob 512, axial movement of the threaded spring base 516increases or decreases the spring preload force of the intensifieradjuster spring 520.

The principles of operation of this adjustment are described in thefollowing.

First, as previously described, the basic principle of operation of theintensifier piston 522 itself can be best characterized as: in order forthe intensifier piston 522 to move downward (“open”), the force(s)acting downward on the small end of the intensifier piston 522 mustequal (or, actually, slightly exceed) the force(s) acting upward on thebig end. For the embodiment as shown in FIGS. 16 and 17, the forceacting upward on the big end of the intensifier piston 522 equals thecross-sectional area of the big end times the pressure in theinternally-pressurized chamber 180. Next, as to the small end of theintensifier piston 522, there are two forces acting downward on it. Oneforce is the compression fluid flow pressure acting on the small end ofthe intensifier piston 522 times the cross-sectional area of the smallend. The other force is the force exerted by the intensifier adjusterspring 520. These two forces together must slightly exceed the upwardforce on the big end of the intensifier piston 522 for the intensifierpiston 522 to move downward (“open”), permitting compression fluid flow.

In accordance with the above principles, turning the intensifieradjuster knob 512 to increase the preload force of the intensifieradjuster spring 520 reduces the compression damping force effectproduced by the adjustable intensifier assembly 510. In fact, dependingon specific parameters including the spring constant (“stiffness”) ofthe intensifier adjuster spring 520, it would be possible to adjust forenough spring preload force to pre-set the intensifier piston 522 in aninitially “open” condition such that the adjustable intensifier assembly510 produced no flow restriction, and thus no compression damping force.Extending this example, a combination of parameters could be determinedaccording to this embodiment of the present invention such that thepressure build-up in the internally-pressurized chamber 180 at somepre-determined point in the compression travel (“stroke”) of the pistonrod 120 exceeded the spring preload force, thus closing the intensifierpiston 522 and thus creating a compression fluid flow restriction and acompression damping effect. In other words, a combination of parameterscould be chosen whereby the compression damping force produced variedfrom zero for the first portion of a compression stroke, to a finite andincreasing value beyond that first portion.

Conversely, turning the intensifier adjuster knob 512 to decrease thepreload force of the intensifier adjuster spring 520 increases thecompression damping force effect produced by the adjustable intensifierassembly 510.

FIGS. 18 and 19 show another exemplary embodiment of the presentinvention. This embodiment incorporates an intensifier piston 540 andpartition assembly 550 similar in structure and function to thatpreviously described in FIGS. 2 and 3. However, the key difference hereis that, in FIGS. 18 and 19 the pressure acting on the large end of theintensifier piston 540 is supplied by an external pressure source (notshown), not by an internal pressure source, such as theinternally-pressurized chamber 180 as it was in previous embodiments.Thus, the pressure required at the small end of the intensifier piston540 to permit compression fluid flow, and therefore the compressiondamping force produced, depends on the external pressure supplied. Thepressure in FIGS. 18 and 19 is supplied to the externally pressurizedchamber 560 through a pressure port 562 fed by an external source (notshown) via a pressure fitting 564. The pressure source, and the mediumcontained in the externally pressurized chamber 560 can be eitherpneumatic or hydraulic. A pneumatic medium and system is preferred wheresimplicity and low cost are dominant factors. An hydraulic medium ispreferred where rapid responsiveness (quick response times) isimportant.

As shown in FIG. 19, a pressure chamber sealing head 566 is held inplace by seal head retaining rings 568, and seals the upper end of theexternally pressurized chamber 560.

One advantage of the embodiment of FIGS. 18 and 19 is the remote,external controllability provided. A system could be designed, forexample, utilizing various sensors on a vehicle. The information fromthese sensors, could be input to an on-board computer module having apre-established algorithm for determining, for any given combination ofinputs, the amount of pressure to be applied to theexternally-pressurized chamber 560, and, thus, the desired level ofcompression damping produced by the damper. A system of this type,utilizing an hydraulic medium, could sense actual vehicle conditions andrespond within milliseconds of real-time, providing enhanced dynamicperformance.

FIGS. 20A and 21 show another exemplary embodiment of the presentinvention. This embodiment is similar to the embodiment of FIGS. 18 and19 except that the externally pressurized chamber 560 is directlypressurized by the spring force of a suspension spring, such as acoil-over spring 570. The upper end of the coil-over spring 570 issupported by a first portion 572 a of a moveable element, such as aspring support ring 572. The lower end of the coil-over spring 570 (notshown) is supported by a ring (not shown) attached to the lower eyelet(not shown, but equivalent to lower eyelet 112 in FIG. 1). The springsupport ring 572 has a second portion 572 b in sealed, slidable contactwith the damper cylinder 150 and the support ring housing 574. The spacebetween the spring support ring 572 and the support ring housing 574, aswell as the space in the externally pressurized chamber 560, is filledwith hydraulic fluid. Note that this hydraulic fluid is entirelydistinct and separated from the hydraulic fluid contained within therest of the damper unit.

The principles of operation of the embodiment of FIGS. 20A and 21 aresimilar to those described for the embodiment of FIGS. 18 and 19. Theonly difference is that in FIGS. 20A and 21 the pressure source is theexternal coil-over spring 570, rather than a generalized pressuresource. In a typical implementation, the compression damping forceproduced by the intensifier assembly 580, from the beginning to the endof a full-travel compression stroke, would begin at a level determinedby the initial preload of the coil-over spring 570, then increaselinearly with the depth of the compression stroke, according to thespring rate (“stiffness”) of the coil-over spring 570. Thischaracteristic could be described as a linearly-increasingposition-sensitive compression damping curve.

In other words, assuming a typical “linear” coil-over spring 570, thecompressed force of the coil-over spring 570 would increase linearly asit was compressed (i.e., decreased in length). This force, directlysupported by the spring support ring 572, would produce a pressure inthe externally pressurized chamber 560 that varied in direct proportion.This pressure, multiplied by the intensifier piston 540, wouldproportionally increase the required pressure to unseat the small end ofthe intensifier piston 540 to permit compression fluid flow, and thuswould proportionally increase the compression damping force produced asa function of the depth of the compression stroke.

FIG. 20B shows an alternate version of the embodiment of FIG. 20A,including addition of a secondary spring 576 in series with the maincoil-over spring 570, a dual-spring adaptor ring 577, and a travel limitretainer ring 579. The location of the travel limit retainer ring 579,and the spring rate of the secondary spring 576 relative to the maincoil-over spring 570, is determined such that, during a compressionstroke of the damper, the spring adaptor ring 577 engages the travellimit retainer ring 579 at some selected point in the travel. Forexample, on a damper with a maximum available stroke of 4-inches, thespring adaptor ring 577 might engage the travel limit retainer ring 579at mid-stroke (i.e., at 2-inches of travel). In this example, the springforce supported by the spring support ring 572, would increase linearlyfor the first 2-inches of travel, as the secondary spring 576 continuedto compress. However, due to the function of the travel limit retainerring 579, for travel beyond this point the secondary spring 576 does notcompress any further (only the main coil-over spring 570 continues tocompress), and thus the spring force supported by the spring supportring 572 does not increase beyond the first 2-inches of travel.

Still referring to FIG. 20B, in accordance with principles previouslydescribed, the compression force transmitted from the first portion 572a of the spring support ring 572 to the second portion 572 b of springsupport ring 572 produces a pressure in the externally pressurizedchamber 560 that varies in direct proportion with the compression force.In turn, this pressure, multiplied by the intensifier assembly 580,proportionately increases the required pressure to unseat the small endof the intensifier piston 540 to permit compression fluid flow. Thus,the compression damping force produced by the intensifier assembly 580as a function of the depth of the compression stroke has the followingcharacteristic shape: it begins at a level determined by the initialspring preload (the force of both springs is equal until the travellimit retainer ring 579 is engaged), it then increases linearly withtravel until the spring adaptor ring 577 engages the travel limitretainer ring 579, at which point it remains constant (“flattens out”)regardless of increasing travel. This type of compression dampingcharacteristic is desirable for certain applications.

FIG. 20C shows another alternate version of the embodiment of FIG. 20A,including addition of a secondary spring 578 in series with the maincoil-over spring 570, a dual-spring adaptor ring 577, and a springtravel limit retainer ring 579. In FIG. 20C the location of the travellimit retainer ring 579, and the spring rate of the secondary spring 578relative to the main coil-over spring 570, is determined such that theadaptor ring 577 is initially in engagement with the travel limitretainer ring 579. Generally, at initial conditions (full extension ofthe damper), the secondary spring 578 has significantly more preloadforce than the main coil-over spring 570. Therefore, during the firstportion of damper travel, only the main coil-over spring 570 compresses.

For example, on a damper with a maximum available stroke of 4-inches,the preload on the secondary spring 578 could be such that only the maincoil-over spring 570 compresses for the first 2-inches of travel. Thespring force supported by the spring support ring 572, would remainconstant for the first 2-inches of travel. However, in this example,beyond this point the secondary spring 576 would begin to compressfurther (both springs compress), and thus the force supported by thespring support ring 572 would increase beyond the first 2-inches oftravel. In contrast to the compression damping characteristic describedabove for the embodiment of FIG. 20B, the embodiment of FIG. 20Cproduces a characteristic shape as follows: it begins at a leveldetermined by the initial preload of the secondary spring 578. Itremains constant at that level (“flat”) until the point is reached wherethe secondary spring 578 begins to compress further, at which point thecompression damping force begins to increase linearly with travel.

By extending the general principles illustrated by FIGS. 20A, 20B, and20C, other possible compression damping force vs. depth of compressionstroke characteristics can be achieved.

FIGS. 22 and 23 show another exemplary embodiment of the presentinvention. This embodiment is similar to the embodiment of FIGS. 20A and21 except that the floating piston 160 (not included or shown in FIGS.22 and 23), as utilized in all previous embodiments, has been entirelyeliminated. This is feasible with the embodiment of FIGS. 22 and 23,since the compressed force of the coil-over spring 570 acts as apressure source on the fluid within reservoir chamber 591, within thedamper unit similar to that previously provided by the floating piston160. As in the exemplary embodiments of FIGS. 20A, 20B, and 20C, thecompression force of spring 570 is transmitted from the first portion572 a of the spring support ring 572 to the second portion 572 b of thespring support ring 572, thereby producing a pressure in the reservoirchamber 560.

In the embodiment of FIGS. 22 and 23, as compared with the embodiment ofFIGS. 20A and 21, the same hydraulic fluid is utilized throughout theentire damper unit, including the intensifier assembly 590 portion.Also, since there is no floating piston and no compressible gas(nitrogen) in this embodiment, the fluid volume displaced by the pistonrod 120 during a compression stroke must be accommodated by downwardmovement of the spring support ring 572, thus providing additionalannular volume for the displaced fluid.

It should be noted, that this also has the effect of somewhat increasingthe “effective spring rate” of the coil-over spring 570. For example,assume a coil-over spring 570 with a spring rate of 300 lbs/in. Alsoassume that the ratio of the annular area of the spring support ring 572to the cross-sectional area of the piston rod 120 is 10-to-1. Assumefurther, for simplicity of this example, that the coil-over spring 570is not at all compressed (has zero pre-load force) at full extension ofthe damper. Now assume a compression stroke that shortens the damperexactly 1-inch. Although the damper is only 1-inch shorter, thecoil-over spring 570 is now 1.1-inches shorter. This results from the1-inch damper stroke, plus the 0.1-inch downward movement of the springsupport ring 572 to accommodate the fluid volume displaced by the pistonrod 120. Thus, the force exerted by the coil-over spring 570 in thisposition is 330 lbs, and it has an “effective spring rate” of 330lbs/in.

One advantage of the embodiment of FIGS. 22 and 23 is the completeelimination of the floating piston 160, the internally-pressurizedchamber 180, and the Schrader valve 190, as included in all previousembodiments. Another advantage, shared with the embodiment of FIGS. 20Aand 21 is the linearly-increasing, position-sensitive compressiondamping effect produced by the intensifier assembly 590.

Note that, generally, the total compression damping force produced bythe embodiment of FIGS. 22 and 23, as well as other embodiments of thepresent invention, will also include the non-linearly-increasing,non-position-sensitive compression damping forces produced byconventional compression valving at the damping piston 140. Thus, theoverall compression damping characteristics will be a combination ofthose produced at the damping piston 140, plus those produced by theintensifier assembly 590.

FIGS. 24, 25 and 26 show another exemplary embodiment of the presentinvention. This embodiment is similar to the embodiment of FIGS. 22 and23 except that an intensifier piston 610 similar to that first shown inFIGS. 4, 5 and 6 is utilized. Another difference is the addition of theintensifier preload spring 612. This enables an increase in thecompression damping effect produced by the intensifier piston 610 nearfull extension, and less relative progressivity throughout the stoke,without requiring an increase in the spring preload of the maincoil-over spring 570. An optional small bleed orifice 614, permittinglimited fluid flow through the intensifier piston 610 when in a closedcondition, thus modifying the operative characteristics of theintensifier assembly, is included. It should be noted that the bleedorifice 614 included here, although not illustrated other embodiments,could also be incorporated in them if desired.

FIG. 27 shows another exemplary embodiment of the present invention.This embodiment is similar to the embodiment of FIGS. 24, 25 and 26except that, rather than the previous intensifier preload spring 612 (asshown in FIG. 25), an intensifier open-bias preload spring 618 isutilized. The effect of the intensifier open-bias preload spring 618 isto maintain the intensifier piston 616 in an open (no flow restriction)position during the early portion (i.e., near-full-extension portion) ofa compression stroke. The intensifier piston 616 does not tend to closeuntil a point in the compression stroke is reached where the internalpressure generated by the coil-over spring 570 overpowers theintensifier open-bias preload spring 618. At this point, the intensifierassembly begins to produce a compression damping effect by requiringpressure at the small end of the intensifier piston 616 in order to keepit open.

A characteristic of having no compression damping created by theintensifier at near-full-extension, but with some beginning andincreasing intensifier-created compression damping occurring somewheremid-stroke can be desirable for certain applications.

Note that, by combining the general principles illustrated by FIGS. 20A,20B, and 20C with those illustrated by FIGS. 25 and 27, a wide varietyof possible compression damping force vs. depth of compression strokecharacteristics can be achieved.

FIG. 28 shows an exemplary embodiment of the present invention asincorporated into the FLOAT-series of air-sprung dampers as produced byFOX Racing Shox of Watsonville, Calif. In this embodiment, an adjustableintensifier assembly 510 essentially identical to that previously shownin FIG. 17 is attached to the main damper assembly 630 by the piggybackeyelet 632. The pressurized air 640 for the air-sprung feature of thedamper is supplied via the Schrader valve 642 as shown.

During a compression stroke of the damper, a volume of hydraulic fluid170 displaced by the piston rod 620 flows upward via the central port622 in the piston rod 620, then flows to the right via a horizontal port634 in the piggyback eyelet 632, then flows downward via an angled port636 into the intensifier assembly 510. The horizontal port 634 isdrilled or otherwise manufactured approximately on-axis with theSchrader valve 642. A press-fit sealing ball 644 is pressed into theentrance of the horizontal port 634 in order to keep the hydraulic fluid170 and the pressurized air 640 entirely separate.

One advantage of the embodiment of FIG. 28 is that, by providing forflow of the displaced hydraulic fluid up through the piston rod 620 toreach the intensifier assembly 510 via ports in the piggyback eyelet 632as shown, the pressure chamber sleeve 660 can be easily and convenientlyunthreaded and completely removed downward from the overall assembly forthe periodic cleaning and maintenance typically required to removeforeign matter which may pass through the dynamic seals during operationand accumulate over time. With a more conventional constructionutilizing an attached reservoir at the bottom end of the damperassembly, removal of the pressure chamber sleeve 660 is significantlymore difficult, since the pressure chamber sleeve 660 as shown cannot beremoved in an upward direction due to interference between the chamberseal assembly 670 and the outer seal assembly 680 portion of thepressure chamber sleeve 660. Thus, additional disassembly, or addedcomplexity of construction, would be required to enable removal of thepressure chamber sleeve 660 if the reservoir was attached at the bottomend of the damper assembly.

FIG. 29 shows another exemplary embodiment of the present invention. Twoof the unique features of this embodiment, as compared with allpreviously shown embodiments, are the outer sleeve 710, and the sealhead check valve assembly 720. A third differentiating feature is thelack of compression valving (symbolic) 142 (not included or shown inFIG. 29) as shown and identified in FIG. 1, and as illustrated in allprevious embodiments. The partition 210 and the intensifier piston 730are similar to those previously shown and described per FIGS. 2 and 3,except for the addition of a bleed screw 257 in the intensifier piston730 for purposes as first previously described relative to FIGS. 4 and5. This feature is important for the embodiment of FIG. 29, since a ventport 270 (not shown or included in FIG. 29) feature such as shown inFIGS. 2 and 3 would be difficult to achieve due to the added outersleeve 710 of FIG. 29.

A primary advantage of the embodiment of FIG. 29 is that, since thedamping piston 140 has no compression ports or valves, no hydraulicfluid flows through the damping piston 140 during a compression stroke.Therefore, the displaced fluid volume during a compression stroke isdetermined by the full cross-sectional area of the damping piston 140,rather than by the much smaller cross-sectional area of the piston rod120, as in previous embodiments. One portion of the displaced fluid, aportion equal to the displaced volume of the piston rod 120, isaccommodated by upward movement of the floating piston 160. The otherportion exits the damper cylinder 150 via the upper flow port(s) 741,then travels downward via the annular space 742 between the dampercylinder 150 and the outer sleeve 710, then re-enters the dampercylinder 150 via the lower flow port(s) 743, which lead to the checkvalve assembly 720 in the seal head 130. The check valve assembly 720opens for flow in the upward direction, allowing the fluid flow tocontinue and to fill the vacated annular space behind the damping piston140 during a compression stroke. Since there is no flow through thedamping piston 140 during a compression stroke, the pressure generatedby the intensifier piston 730 acts on the full cross-sectional area ofthe damping piston 140. Thus, relatively large compression dampingforces can be produced with this embodiment at significantly lowerinternal pressures than in previous embodiments.

In FIG. 29, the check valve assembly 720 permits fluid flow in theupward direction only. Thus, during a rebound stroke, the check valveassembly 720 is closed, and the fluid pressure created between thedamping piston 140 and the seal head 130 cannot escape through the sealhead 130. Therefore, the desired rebound damping forces are created bythe damping piston 140 and the rebound valving 141.

FIGS. 30 and 31 show another exemplary embodiment of the presentinvention. This embodiment is somewhat similar to the previousembodiment shown in FIGS. 16 and 17, except that the intensifierassembly 750 is oriented horizontally within the piggyback eyelet 760structure leading to the reservoir assembly 770. Besides the differentlocation, the other key difference relative to the embodiment of FIGS.16 and 17 is that here the intensifier adjuster spring 754 engages thelarge end of the intensifier piston 752, rather than the small end. Thenet effect of this is that, in FIGS. 30 and 31, an adjustment thatincreases the preload force on the intensifier adjuster spring 754increases the compression damping force produced by the intensifierassembly 750. In contrast, in FIGS. 16 and 17, an adjustment thatincreases the preload force of the intensifier adjuster spring 520decreases the compression damping force produced. There is no particularadvantage or disadvantage to either construction; the differences aresimply pointed out here for clarity.

In the embodiment of FIGS. 30 and 31, the pressure from theinternally-pressurized chamber 180 below the floating piston 160 reachesthe large end of the intensifier piston 752 via a pressure port 762 inthe piggyback eyelet 760. Fluid flow due to displacement of the pistonrod 120 during compression and rebound strokes flows into and out of theupper portion of the reservoir cylinder 772 via the flow port 764.

FIGS. 32 and 33 show another exemplary embodiment of the presentinvention. This embodiment differs from the previous embodiment of FIGS.30 and 31 in two basic respects. First, the intensifier assembly 780,rather than being oriented horizontally as in the previous embodiment,is oriented at a small angle from horizontal. This provides nosignificant performance benefits, but is shown simply as an illustrationof one of the configuration possibilities available with this embodimentwhich may offer easier access to the intensifier adjuster knob 512 formaking adjustments to the damper as installed in a particularapplication.

Secondly, the embodiment of FIGS. 32 and 33 differs from the previousembodiment of FIGS. 30 and 31 by the addition of the compression flowbleed adjuster assembly 790. The basic mechanism of this assembly,whereby rotation of the bleed adjuster knob 792 produces translation ofthe tapered bleed adjuster needle 794, is similar to the mechanismutilized in the adjustable intensifier assembly 510, as best seen anddescribed previously relative to FIG. 17. The compression flow bleedadjuster assembly 790 provides independent tuning of compression bleedflow of the damper. This can be an important tuning element in manydamper applications. Compression bleed flow occurs in parallel with anycompression flow through the intensifier assembly 780.

FIG. 34 shows an overall view of a front suspension fork 800 which couldbe used on a bicycle or motorcycle (not shown). FIGS. 35, 36, and 37show an exemplary embodiment of the present invention as incorporatedinto the suspension fork 800 of FIG. 34.

FIGS. 35 and 36 show a fork leg assembly 810, in part comprised of afork crown (partial view) 812, a fork upper tube 814, a fork lower tube816, a Schrader valve 819, air 820, and hydraulic fluid 830 filled to anapproximate level 831 as shown. In addition, the fork leg assembly 810comprises a damper assembly 840 as shown in isolation in FIG. 36. Theupper portion of the damper assembly 840 shown in FIG. 36 includes apiston rod 842, a damping piston 844, a damper cylinder 850 andhydraulic fluid 830, a construction sometimes referred to as a dampercartridge assembly.

An intensifier assembly 860 in the lower portion of the damper assembly840 shown in FIG. 36 comprises an exemplary embodiment of the presentinvention, and is best seen in FIG. 37.

FIG. 37 shows the intensifier assembly 860 which includes a partition870, an intensifier housing 880, an intensifier piston 890, anintensifier preload spring 892, an adjuster rod 894, and an adjusterknob 896.

The principles of operation of the intensifier assembly 860 of FIG. 37are similar to those previously shown and described for previousembodiments. During a compression stroke of the suspension fork 800, thepiston rod 842 displaces a volume of the hydraulic fluid 830 in thedamper cylinder 850. In order for the compression stroke to occur, thedisplaced fluid must exit the damper assembly. For the structure shownin FIG. 37, this can only occur when the pressure in the hydraulic fluid830 above the partition 870, acting on the area of the small end of theintensifier piston 890, overcomes the upward forces acting on theintensifier piston 890, thus causing the intensifier piston 890 to movedownward, allowing downward fluid flow through the compression flow port872.

There are two upward forces acting on the intensifier piston 890. First,there is the upward force applied by the intensifier preload spring 892.Second, there is the internal pressure in the air 820, which iscommunicated by the hydraulic fluid exterior to the damper cylinder 850up through the bottom of the intensifier assembly 860 via the lowerbi-directional flow port(s) 862, and which acts on the cross-sectionalarea of the large end of the intensifier piston 890 to produce thesecond upward force.

Thus, identical in principle to previously-described embodiments of thepresent invention, a relatively large hydraulic fluid pressure increaseis created by the adjustable intensifier assembly 860 during acompression stroke. This pressure increase, acting on thecross-sectional area of the piston rod 842 produces a compressiondamping force in the suspension fork 800.

The fork leg assembly 810 of FIG. 35 can be assembled with a desiredvolume of air 820 at atmospheric pressure, or it can be supplied withpressurized air (or other compressible gas, such as nitrogen) via aSchrader valve 819. In either case, as a compression stroke of thesuspension fork 800 proceeds, the volume of the air 820 in the fork legassembly 810 is progressively reduced (compressed), resulting in aprogressively-increasing internal pressure. This increasing internal airpressure, acting through the intensifier assembly 860, produces aprogressive increase in the compression damping force of the suspensionfork 800. Thus, a progressive, position-sensitive compression dampingforce is produced.

However, it should be noted again that, similar to descriptionsregarding previous embodiments of the present invention, compressiondamping forces in the suspension fork 800 are generally also produced atthe damper piston 844. Thus, in general, the total compression dampingcharacteristics produced by various embodiments of the present inventionresult from a combination of the compression damping forces created byvalving at the damper piston (for example, 844 in FIG. 36) plus thecompression damping forces resulting from pressure increases produced bythe intensifier assembly (for example, 860 in FIG. 36) acting on thecross-sectional area of the piston rod (for example, 842 in FIG. 36).

Although the present invention has been explained in the context ofseveral exemplary embodiments, minor modifications and rearrangements ofthe illustrated embodiments may be made without departing from the scopeof the invention. For example, but without limitation, although theexemplary embodiments described intensifier pistons with bleed or ventprovisions to eliminate pressure in the space between the small andlarge ends of the intensifier pistons, the principles taught may also beutilized in damper embodiments without these provisions. In addition,although the exemplary embodiments were described in the context ofvehicular applications, the present damper may be modified for use innon-vehicular applications where dampers may be utilized. Furthermore,it is contemplated that various aspects and features of the inventiondescribed can be practiced separately, combined together, or substitutedfor one another, and that a variety of combination and subcombinationsof the features and aspects can be made and still fall within the scopeof the invention. Accordingly, the scope of the present invention is tobe defined only by the appended claims.

1. A damper operable between a compressed position and an extendedposition, comprising: a compression chamber containing hydraulic fluidand having a volume varying in response to operation of the damperbetween the positions; a reservoir chamber; and an intensifier valve,comprising a piston: having a first surface in fluid communication withthe compression chamber and a second surface in fluid communication withthe reservoir chamber, operable between: an open position where theintensifier valve provides fluid communication between the chambers, anda second position where the intensifier valve restricts fluid flow fromthe compression chamber to the reservoir chamber, wherein a first areaof the first surface is less than a second area of the second surface.2. The damper of claim 1, wherein: the reservoir chamber is pressurized,the second position is a closed position where the intensifier valvesubstantially prevents fluid flow from the compression chamber to thereservoir chamber, the intensifier piston is biased toward the closedposition by a second force generated by pressure in the reservoirchamber exerted on the second area, and the intensifier piston isoperable from the closed position to the open position in response to afirst force generated by pressure in the compression chamber exerted onthe first area exceeding the second force.
 3. The damper of claim 2,wherein the intensifier valve further comprises: a housing having anopening formed therethrough and having a longitudinal port formedtherethrough a partition: having a compression port formed therethrough,and having a rebound port formed therethrough, and a check valveoperable to prevent flow through the rebound port from the compressionchamber to the reservoir chamber and to allow flow through the reboundport from the reservoir chamber to the compression chamber, wherein: theintensifier piston extends through the opening and closes thecompression port in the closed position, the compression port is influid communication with the compression chamber, and the housing portis in fluid communication with the reservoir chamber, the rebound port,and the compression port when the intensifier piston is in the openposition.
 4. The damper of claim 3, further comprising: a dampercylinder having a wall and a longitudinal bore therethrough surroundedby the wall, a piston rod at least partially disposed in the dampercylinder bore and longitudinally movable relative to the dampercylinder; a damping piston: disposed in the damper cylinder bore,longitudinally coupled to the piston rod, and defining a first end ofthe compression chamber wherein: the partition defines a second end ofthe compression chamber, and the housing defines a first end of thereservoir chamber.
 5. The damper of claim 4, wherein the housing isformed integrally with or longitudinally coupled to the damper cylinder,and the partition is disposed in the damper cylinder bore and islongitudinally coupled to the damper cylinder.
 6. The damper of claim 4,further comprising: a reservoir cylinder having a wall and alongitudinal bore therethrough surrounded by the wall; and an eyeletlongitudinally coupled to the damper cylinder and having a port formedtherethrough in fluid communication with the damper cylinder bore andthe reservoir cylinder bore.
 7. The damper of claim 6, wherein thehousing is formed integrally with or longitudinally coupled to thereservoir cylinder, and the partition is disposed in the reservoircylinder bore and is longitudinally coupled to the reservoir cylinder.8. The damper of claim 2, wherein the intensifier valve furthercomprises: a partition: having an opening formed therein, having a portformed therethrough, and having a rebound port formed therethrough, anda check valve operable to prevent flow through the rebound port from thecompression chamber to the reservoir chamber and to allow flow throughthe rebound port from the reservoir chamber to the compression chamber,wherein: the intensifier piston: is disposed in the opening, has acompression port formed therethrough, and closes the partition port inthe closed position, the partition port is in fluid communication withthe compression chamber, and the compression port is in fluidcommunication with the reservoir chamber and the partition port when theintensifier piston is in the open position.
 9. The damper of claim 8,further comprising: a damper cylinder having a wall and a longitudinalbore therethrough surrounded by the wall, a piston rod at leastpartially disposed in the damper cylinder bore and longitudinallymovable relative to the damper cylinder; a damping piston: disposed inthe damper cylinder bore, longitudinally coupled to the piston rod, anddefining a first end of the compression chamber, wherein the partitiondefines a second end of the compression chamber and a first end of thereservoir chamber.
 10. The damper of claim 9, wherein the partition isformed integrally with or longitudinally coupled to the damper cylinder.11. The damper of claim 9, further comprising: a reservoir cylinderhaving a wall and a longitudinal bore therethrough surrounded by thewall; and an eyelet longitudinally coupled to the damper cylinder andhaving a port formed therethrough in fluid communication with the dampercylinder bore and the reservoir cylinder bore.
 12. The damper of claim11, wherein: the partition is formed integrally with the reservoircylinder, or the partition is longitudinally coupled to the reservoircylinder and disposed in the reservoir cylinder bore.
 13. The damper ofclaim 2, wherein the intensifier valve further comprises: a partition:having an opening formed therethrough, having a compression port formedtherethrough, and having a rebound port formed therethrough, and a checkvalve operable to prevent flow through the rebound port from thecompression chamber to the reservoir chamber and to allow flow throughthe rebound port from the reservoir chamber to the compression chamber,wherein: the intensifier piston extends through the opening and closesthe compression port in the closed position, and the compression port isin fluid communication with the compression chamber and the reservoirchamber when the intensifier piston is in the open position.
 14. Thedamper of claim 13, further comprising: a damper cylinder having a walland a longitudinal bore therethrough surrounded by the wall, a pistonrod at least partially disposed in the damper cylinder bore andlongitudinally movable relative to the damper cylinder; a dampingpiston: disposed in the damper cylinder bore, longitudinally coupled tothe piston rod, and defining a first end of the compression chamberwherein the partition defines a second end of the compression chamberand a first end of the reservoir chamber.
 15. The damper of claim 14,further comprising: a reservoir cylinder having a wall and alongitudinal bore therethrough surrounded by the wall; and an eyeletlongitudinally coupled to the damper cylinder and having a port formedtherethrough in fluid communication with the damper cylinder bore andthe reservoir cylinder bore.
 16. The damper of claim 15, wherein: thepartition is longitudinally coupled to the reservoir cylinder anddisposed in the reservoir cylinder bore.
 17. The damper of claim 1,further comprising: a damper cylinder having a wall and a longitudinalbore therethrough surrounded by the wall, a piston rod at leastpartially disposed in the damper cylinder bore and longitudinallymovable relative to the damper cylinder; a damping piston: disposed inthe damper cylinder bore, longitudinally coupled to the piston rod, anddefining a first end of the compression chamber.
 18. The damper of claim17, further comprising: a rebound chamber containing the hydraulicfluid; a seal head: longitudinally coupled to the damper cylinder,having a longitudinal opening therethrough, and defining a first end ofthe rebound chamber, wherein the piston rod is disposed through the sealhead opening and the damping piston defines a second end of the reboundchamber.
 19. The damper of claim 18, wherein the damping pistoncomprises: a compression valve operable to restrict fluid flow from thecompression chamber to the rebound chamber, and a rebound valve operableto restrict fluid flow from the rebound chamber to the compressionchamber.
 20. The damper of claim 18, further comprising: an outer sleevesurrounding the damper cylinder; an annular space defined between theouter sleeve and the damper cylinder; an upper flow port formed throughthe wall of the damper cylinder and in fluid communication with theannular space and the reservoir chamber; a lower flow port formedthrough the wall of the damper cylinder and in fluid communication withthe annular space and a check valve; and the check valve disposed in theseal head and operable to allow from the annular space to the reboundchamber and to prevent flow from the rebound chamber to the annularspace, wherein the damping piston comprises a rebound valve operable torestrict fluid flow from the rebound chamber to the compression chamber.21. The damper of claim 17, wherein the intensifier valve is disposed inthe damper cylinder and defines a first end of the reservoir chamber.22. The damper of claim 21, wherein: the reservoir chamber contains thehydraulic fluid and a gas, and the damper further comprises: an eyeletlongitudinally coupled to the damper cylinder and defining a second endof the reservoir chamber; and a floating piston disposed in the dampercylinder and dividing the reservoir chamber into a hydraulic fluidportion and a gas portion.
 23. The damper of claim 17, furthercomprising: a reservoir cylinder having a wall and a longitudinal boretherethrough surrounded by the wall; and an eyelet longitudinallycoupled to the damper cylinder and having a port formed therethrough influid communication with the damper cylinder bore and the reservoircylinder bore, wherein the intensifier valve is disposed in thereservoir cylinder and defines a first end of the reservoir chamber. 24.The damper of claim 23, wherein: the reservoir chamber contains thehydraulic fluid and a gas, and the damper further comprises a floatingpiston disposed in the reservoir cylinder and dividing the reservoirchamber into a hydraulic fluid portion and a gas portion.
 25. The damperof claim 1, wherein the first area is substantially less than the secondarea.